48 INFECTIOUS AND PARASITIC DISEASES. 



hygienic conditions under which exposed individuals 

 live are especially bad. Just such a condition as de- 

 scribed pertained in the great military camps during the 

 Spanish-American war, and the commission, appointed 

 by the Surgeon- General of the army to report on the 

 prevalence of typhoid fever among these troops, 

 ascribed the stupendous morbidity to a few factors 

 chiefly, not the least important of which was the pres- 

 ence of typhoid bacilli in the dust surrounding the 

 camps. 



Another way in which germs in the soil may infect 

 persons, and this is true particularly of the typhoid 

 bacillus and the cholera spirillum, is for the microbes 

 to become attached to vegetables grown in the soil, 

 especially if these vegetables are such as are usually 

 consumed raw. However, whilst the majority of 

 pathogenic bacteria in the soil may be regarded as 

 accidental contaminations, there are a few whose 

 natural habitat is the ground. These are the tetanus 

 bacillus, the bacillus of gaseous edema, and the bacillus 

 of malignant edema. In countries where bubonic 

 plague is epidemic, the specific bacillus (bacillus 

 pestis) seems to find a favorable environment in the 

 ground. 



As has been said, water is most frequently 



Water, polluted by the washings from contami- 

 nated soil. The pathogenic bacteria most 

 feared in water or ice are the cholera spirillum and the 



